The present invention relates to exhaust gas treatment devices for internal combustion engines and the like, and in particular to an insulated housing construction therefor.
Exhaust gas treatment devices, such as catalytic converters, evaporative emission devices, hydrocarbon scrubbing components and the like, are well known in the art, and are used to treat exhaust gas from internal combustion engines, such as those associated with automobiles, trucks, boats and other vehicles. These exhaust gas treatment devices typically employ catalysts supported by substrates in a housing to catalytically treat the stream of exhaust gas. Due to the high temperature of the exhaust gas, and the normally preferred hot operating temperature of the exhaust gas treatment mechanism, such devices are usually separated or otherwise thermally insulated from adjacent components of the vehicle.
A combination exhaust manifold and catalytic converter, or “maniverter”, such as that disclosed in U.S. Pat. No. 6,555,070, has been developed for use in automobiles, wherein the component is positioned within the engine compartment of the vehicle. While maniverters provide a very compact construction, they are relatively expensive to manufacture, and emit substantial additional heat in the engine compartment, and therefore must include some form of heat shield to prevent degradation and/or damage to adjacent components of the vehicle. Metal shields, mounting brackets and fasteners, etc. have been used to shield the heat of prior art exhaust treatment devices, particularly in two-stage or dual substrate configurations, wherein the medial portions of the devices, through which the gas sensors extend, normally have a single wall construction, and are not internally insulated from adjacent components in the engine compartment of the vehicle. While such devices do reduce some radiation heat transfer, they are not very effective in reducing convection heat transfer. Because the gas sensors associated with exhaust gas treatment devices typically protrude radially outwardly from the components, the associated areas of the housing members are difficult to shield from heat transfer to adjacent vehicle components.
Hence, the need exists for an exhaust gas treatment device which has a compact size, efficiently and effectively treats exhaust gas emissions, is thermally insulated, and has an uncomplicated construction which is economical to manufacture.